1. Field of the Invention
The present invention relates to a compact zoom lens system of a two-lens-group arrangement having a short back focal distance, which is suitable for a lens-shutter camera.
2. Description of the Prior Art
Unlike a zoom lens system of a single lens reflex (SLR) camera which requires space to accommodate a quick-return mirror behind the photographing lens system, a zoom lens system of a compact camera does not require a long back focal distance. As a zoom lens system for a lens-shutter camera having little constraints on the back focal distance, a telephoto-type zoom lens system is suitable for achieving further compactness of a camera. Here, note that a telephoto-type zoom lens system includes a front lens group having a positive power (hereinafter, positive front lens group) and a rear lens group having a negative power (hereinafter, negative rear lens group) in this order from the object; and zooming is performed by varying the distance between the positive front lens group and the negative rear lens group.
However, if an attempt is made to achieve a zoom ratio of 3 or more in this telephoto-type zoom lens system, a zoom lens system of a three-lens-group arrangement which is a modification of a telephoto-type zoom lens system has to be employed. Consequently, the diameter of the positive front lens group is increased, and the structure and the size of the zoom lens system become more complicated and larger.